1. Field of the Invention
This invention relates to a drive system and more particularly to measuring the rotational angle of a drive system.
2. Description of Related Art
Drive systems such as those used, for example, as servo motors, consist of an electric motor and a rotational angle measuring system coupled to the electric motor which measures values such as the angular position, the rpm, and/or the rotary acceleration to regulate the electric motor. The electric motor may consist of a rotor, a stator, and windings. The motor shaft may be mounted at each end of the motor in a roller bearing. The roller bearing that supports the drive shaft is usually referred to as the A bearing, while the roller bearing that supports the opposite end is termed the B bearing. Rotary angle measuring systems have a measuring system shaft that is coupled non-rotatably with the motor shaft and has an angular measure. A stator of the rotary angle measuring system includes a scanner that scans the angular measure. The stator of the rotary angle measuring system is supported non-rotatably by a stator coupling relative to the stator of the electric motor.
In known drive systems (for example DE 44 46 243 C1, DE 33 01 205 C2, GB 2 117 572 A) the measuring system shaft of the rotary angle measuring system is supported in at least one roller bearing of the stator of the rotary angle measuring system. The measuring system shaft is coupled rigidly with the motor shaft. The radial and axial movements of the motor shaft are consequently transferred to the measuring system shaft. Errors in axial alignment between the motor shaft and the measuring system shaft produce wobbling movements of the measuring system shaft. The stator of the rotary angle measuring system that is mounted on the measuring system shaft by means of the roller bearings must follow all of these movements. The stator coupling must therefore be flexible both axially and radially, but must support the stator of the rotary angle measuring system without twisting.
It is desirable to provide a drive system that does not exhibit all of the problems described above and that can be manufactured economically and take up little space.